1. Technical Field
The present invention relates generally to a method, system, and product for testing electronic circuits, and more particularly to a method, system, and product for testing the gain versus frequency of continuous-time or discrete-time devices that are included within an electronic circuit, where the device is tested utilizing an automatic gain control (AGC) circuit that is preexisting within the electronic circuit.
2. Description of the Related Art
Magnetic media is effectively used to store digital data in applications such as tape or disk storage systems. Data is written onto the magnetic material by a write head. The write head converts a current signal containing the digital information into flux patterns, which are written as field transitions onto the magnetic material. The data is retrieved when the magnetic media is passed by a read head. The read head passes over the magnetic medium and transduces the magnetic transitions into pulses in an analog read signal, which are then decoded by read channel circuitry to reproduce the digital sequence.
Read channels often include a continuous-time devices, such as a filter for filtering signals and amplification for adjusting the amplitude of the signal read from a magnetic tape. A filter employed in a read channel must generally be capable of accommodating variations in the data rate of the readback signals transmitted through the read channel. The ability to precisely tune such a filter is therefore of particular importance. Gain circuitry must also be precisely set to optimize the dynamic range of the signal throughout the read channel.
In order to more precisely adjust these devices, such as by tuning the frequency response of a filter or the gain of an amplifier, it is necessary to characterize the operating conditions of the devices. In the prior art, in order to characterize the operating conditions of a circuit, an input test signal was provided to the circuit and the output generated by the circuit was analyzed by a separate test circuit, which was typically an off-chip tester. This approach to characterizing a circuit requires expensive off-chip tester features and control and requires time-consuming post processing of the input and output signals for the characterization to be complete. In read channel application, the preexisting variable gain amplifier and AGC loop can be used to greatly simplify the existing techniques for the device characterization.
Therefore, a need exists for a method, system, and product for testing devices that are included within an electronic circuit in a timely cost efficient manner, utilizing circuit elements that already exist within the electronic circuit.